Gelled nitromethane explosive containing fluid encapsulations



United States Patent Commercial Solvents Corporation, New York, N.Y., a

corporation of Maryland No Drawing. Filed Aug. 11, 1966, Ser. No. 571,735 12 Claims. (Cl. 102-27) This invention relates to stable, sensitized explosive compositions comprising nitromethane and as sensitizer, resin balloons. In a particular aspect, this invention relates to stable, gelled explosive compositions comprising nitromethane and as sensitizer, resin balloons. In a further aspect, this invention relates to stable, gelled explosive compositions in the form of the explosive core for detonator cord comprising nitromethane and as sensitizer, a finely divided, air-entrapping material. In a still further aspect, this invention relates to novel detonating cord having a stable, sensitized explosive core in gelled form comprising nitromethane and a finely divided airentrapping material.

Explosive compositions comprising nitromethane and a sensitizer for the nitromethane are well-known and are used in a variety of applications. Sensitized nitromethane explosive compositions are used in either the normally liquid form or in gelled form. Normally liquid nitromethane compositions are readily converted to semi-solid or thickened form typically referred to as gelled form nitromethane by incorporation with a suitable gelling agent for the nitromethane, such as for example nitrocellulose. Other gelling or thickening agents for nitromethane are disclosed in application Ser. No. 446,736, filed Apr. 8, 1965, for L. R. Jones and in US. Patent 2,954,- 350, issued Sept. 27, 1960 to R. F. Purcell.

Numerous materials are known to sensitize nitromethane, of which the nitromethane soluble amines, in particular lower alkylimine, arylalkyleneamine, monoethanolamine, alkylphosphorousamide, aryldiamine, aminopyridine, N,N'-diethyl-p-phenylenediamine, hydrazine and alkylarylidiamine are generally most effective When nitromethane containing explosive compositions sensitized for detonation with conventional blasting caps are desired.

Despite the effectiveness of the aforementioned nitromethane soluble amines in sensitizing nitromethane, explosive compositions comprising nitromethane and one or more of said amines present serious problems with respect to stability. Nitromethane explosive compositions sensitized with the aforestated amines are generally unstable and decompose after storage for several days. The instability of the explosive compositions is a particular drawback when the compositions are used in gelled form as the explosive material in the explosive core of d t at cord. Detonator cord typically comprises an explosive core in the form of a solid explosive composition, a sheath, e.g. a textile sheath for the explosive core and an outer cover of metal or a thermoplastic material such as polyvinyl chloride or polyethylene. When nitromethane sensitized by the aforestated amines is used in gelled form as the explosive core of detonator cord, pressure from gases formed from the decomposition of the nitromethane often causes ballooning or rupture of the outer covering of the detonator cord.

It is an object of the present invention to provide stable, sensitized nitromethane explosive compositions.

It is a further object of the present invention to provide stable, sensitized nitromethane explosive compositions in gelled form.

It is a still further object of the present invention to provide stable, gelled, sensitized nitromethane explosive composition in the form of the explosive core for detonator cord.

It is an additional object of the present invention to provide a detonator cord having a stable, sensitized explosive cord.

Other objects and advantages of the present invention will be apparent from the specification and appended claims.

The present invention in a first embodiment resides in the discovery that sensitized nitromethane explosive compositions which are stable against decomposition are obtained by incorporating into the explosive composition a sensitizing amount of resin balloon.

The present invention in a second embodiment resides in the discovery that gelled, sensitized nitromethane explosive compositions which are stable against decomposition are obtained by incorporating into the gelled explosive composition a sensitizing amount of resin balloon.

The present invention in a third embodiment resides in the discovery that gelled, sensitized nitromethane eX- plosive compositions which are stable against decomposition and suitable as explosive core of detonator cord are obtained by incorporating into the gelled explosive composition a sensitizing amount of a finely divided, air-entrapping material. Examples of such finely divided, airentrapping materials include bagasse, wood flour, ground balsa, resin balloons and the like. Because of the excellent results obtained therewith resin balloons are preferred.

The resin balloons of use in the explosive compositions of the present invention are water insoluble and nitromethane insoluble, thin-walled, hollow, spherical balloons of a polymerized thermosetting resin-selected from the group consisting of urea-formaldehyde and phenolformaldehyde. The resin balloons are of low density and small particle size. Typical resin balloons have a bulk density of less than 0.3 gr./cc. and a diameter of from about 2 to about 360 microns. Resin balloons are more fully described in US. Patent 3,101,288 to Coursen et al. issued Aug. 20, 1963. Such resin balloons are commercially available.

The amount of resin balloons required to sensitize mtromethane explosive compositions will vary and will depend chiefly on the use desired for the particular explosive composition. Typically suitable amounts of resin balloons in the explosive compositions of the present invention are in the range of from about 0.1 to about 20% by weight based on the weight of the explosive composition. While amounts greater than 20% by weight of resin balloons may be included in the explosive compositions of the present invention, such amounts are considered excess. For most applications and in particular when the explosive composition is used in gelled form as the eX- plosive core of detonator cord, amounts of resin balloons 1n the range of from about 1.5 to about 10% are preferred.

Explosive compositions comprising nitromethane and resin balloons may be prepared in any suitable manner, as for example by mixing the resin balloons with the nitromethane. It is Well understood in the art that high temperatures during mixing should be avoided.

It is sometimes desirable to include one or more additives in the explosive compositions of the present invention in order to enhance or alter their performance in particular applications. For example, it is often desirableto include a fuel and/or an oxidizer in the explosive compositions of the present invention.

Examples of fuels include elemental carbon in various forms, such as carbon black, graphite and the like; aliphatic hydrocarbons such as pentane,-octane, dodecane and .cyclohexane; organic polymers such as liquid and solid polymers of ethylene and propylene; organic ketones such as diethyl ketone, ethyl butyl ketone, cyclohexanone and the like; and alkyl ethers of saturated glycols such as the monomethyl ether of ethylene glycol and the monoethyl ether of ethylene glycol and the like.

Examples of oxidizers include ammonium nitrate, sodium nitrate, lithium nitrate and the like.

Examples of other additives include guanidine nitrate, pentaerythritol tetranitrate, and cyclotrimethylene trinitramine.

The explosive compositions of the present invention may be used in either the normally liquid or in gelled form. Normally liquid nitromethane is readily converted to gelled form by incorporation of a suitable thickening or gelling agent into the nitromethane as previously indicated.

The explosive compositions of the present invention have a variety of uses well-known to the art. As previously indicated, gelled explosive compositions of the present invention are especially useful as the explosive core of detonator cord. The compositions of the present invention also are particularly useful in oil wells to fracture oil bearing formations.

The invention will be understood more fully by reference to the following specific examples. It is understood that the examples are presented for the purpose of illustration only and are not intended as a limitation of the invention.

In the examples the resin balloons used were prepared from phenol-formaldehyde resins and were commercially sold by the Bakelite Company, a Division of Union Carbide Corporation under the trademark Microballoons. The resin balloons were of small particle size and low bulk density. Microballoons manufactured from ureaformaldehyde resins are also commercially available and if desired can be substituted for Microballoons manufactured from phenol-formaldehyde resins.

Example 1 Tests were conducted to show the effectiveness of resin balloons in sensitizing nitromethane explosive compositions. The sensitized explosive compositions used in the tests designated A-G inclusive in the table below were prepared by blending resin balloons into a gelled nitromethane explosive composition prepared by blending 95 parts by weight nitromethane with 5 parts by weight nitrocellulose. The composition used in test H contained no resin balloons and was prepared by blending 95 parts by weight nitromethane with 5 parts by weight nitrocellulose.

In each test 100 grams of nitromethane explosive composition was placed in a 2" diameter plastic cup. The cup was placed behind a safety shield and was detonated by a No. 6 or No. 8 blasting cap. The blasting caps were commercially sold by Atlas Powder Company. The results of the tests are set forth in the table which follows:

The above results show the effectiveness of resin balloons as sensitizers for nitromethane.

Example 2 A detonator cord was prepared by loading a piece of polyethylene tubing 14 inches in length and 4; inch in diameter (inside) with a gelled, sensitized nitromethane explosive composition comprising 95 parts by weight nitromethane, 5 parts by weight nitrocellulose and 5 parts Q by weight resin balloons. The cord was detonated with a No. 6 blasting cap. Detonation of the entire cord was obtained. The rate of detonation was in excess of 18,000 feet per second.

Example 3 The following is an example of a stable, sensitized nitromethane explosive composition.

Parts by weight Nitromethane (liquid) Phenol-formaldehyde resin balloons 5 Example 4 The following is an example of a stable, sensitized nitromethane explosive composition in gelled form.

Parts by weight Nitromethane Carbon black 40 Ammonium nitrate 200 Nitrocellulose 6 Phenol-formaldehyde resin balloons 10 Example 5 The following is an example of a stable, sensitized nitromethane explosive composition in gelled form suitable for use as the explosive core in detonator cord.

nitromethane explosive composition in gelled form suitable for use as the explosive core in detonator cord.

Parts by weight Nitromethane 95 Nitrocellulose 5 Ba gasse 8 Since many embodiments of this invention may be made and since many changes may be made in the embodiments described, the foregoing is to be interpreted as illustrative only and the invention is defined by the claims appended hereto.

I claim:

1. An explosive composition comprising nitromethane and a sensitizing amount of a water-insoluble and nitromethane-insoluble polymerized thermosetting resin selected from the group consisting of phenol-formaldehyde and urea-formaldehyde resins in the form of thin-walled, hollow, spherical balloons.

2. A gelled explosive composition comprising nitromethane, a gelling agent for the nitromethane and a sensitizing amount of water-insoluble and nitromethaneinsoluble polymerized thermosetting resin selected from the group consisting of phenol-formaldehyde and ureaformaldehyde resins in the form of thin-walled, hollow, spherical balloons.

3. The composition of claim 2 wherein the said balloons have a bulk density of less than about 0.3 g. per cc. and a diameter in the range of from about 2 to about 360 microns.

4. The composition of claim 2 wherein the amount of said balloons in the said composition is in the range of from about 0.1 to about 20% by weight based on the weight of the composition.

5. The composition of claim 2 wherein the said gelling agent is nitrocellulose.

6. The composition of claim 2 in the form of an explosive core for detonator cord.

7. The composition of claim 6 wherein the spherical balloons have a bulk density of less than about 0.3 g.

per cc. and a diameter in the range of from about 2 to about 360 microns.

8. The composition of claim 6 wherein the amount of said spherical balloons in said composition is in the range of from about 1.5 to about 10% by weight based on the weight of the composition.

9. A detonator cord including an explosive core, a sheath for said core and a cover for said sheath, the composition of said core comprising nitromethane, a gelling agent for said nitromethane and a sensitizing amount of a finely divided, air-entrapping material.

10. The detonator cord of claim 9 wherein the finely divided, air-entrapping material is a water-insoluble and nitromethane-insoluble, polymerized thermosetting resin selected from the group consisting of phenol-formaldehyde and urea-formaldehyde resins in the form of thinwalled, hollow, spherical balloons.

11. The detonator cord of claim 10 wherein the said balloons have a bulk density of less than 0.3 g. per cc. and a diameter in the range of from about 2 to about 360 microns.

12. The detonator cord of claim 10 wherein the amount of said resin balloons in the composition of said core is in the range of from about 0.1 to about 20% by weight based on the weight of the composition.

References Cited UNITED STATES PATENTS 3,035,948 5/1962 Fox 14989 X 3,143,446 8/1964 Berman 149-19 X 3,204,560 9/1965 Gustavson 149-2 X 3,242,022 3/ 1966 Atkins et a1. 149-89 OTHER REFERENCES Bogin et al.: Ind. Eng. Chem., vol. 34, No. 9, pp. 1091 to 1096 (1942).

Urbanski: Chemistry and Technology of Explosives, The Macmillan Company, New York, 1964, pp. 584 to 586.

DEWAYNE RUTLEDGE, Primary Examiner.

CARL D. QUARFORTH, Examiner.

L. A. SEBASTIAN, Assistant Examiner. 

1. AN EXPLOSIVE COMPOSITION COMPRISING NITROMETHANE AND A SENSSITIZING AMOUNT OF A WATER-INSOLUBLE AND NITROMETHANE-INSOLUBLE POLYMERIZED THERMOSETTING RESIN SELECTED FROM THE GROUP CONSISTING OF PHENOL-FORMALDEHYDE AND UREA-FORMALDEHYDE RESINS IN THE FORM OF THIN-WALLED, HOLLOW, SPHERICAL BALLOONS. 